1. Field of the Invention
The present invention relates to a trajectory display device for displaying a trajectory of a tool axis.
2. Description of the Related Art
Machine tools carry out machining by changing the relative position of a tool relative to an object to be machined along a plurality of drive axes. In machine tools with drive axes including a rotational axis, machining is carried out while changing the posture of the tool with respect to the object to be machined. In such machine tools, calculating and displaying the tool tip point trajectories based on the position information of each of the drive axes and the configuration of the machine tool is known.
Japanese Patent No. 4689745 discloses a machine tool which calculates three-dimensional coordinate values for the tool tip as viewed from a coordinate system fixed to a workpiece and displays three-dimensional trajectory of a tool tip using three-dimensional coordinate values. In this machine tool, the start point of a tool vector is a point on the tool central axis separated from the tip of the tool by a preset distance to the root thereof. The machine tool calculates the three-dimensional coordinate value of the start point of the tool vector as viewed from the coordinate system fixed to the workpiece, using the actual position information and the information about the mechanical structure of the machine tool. Further, the line connecting the tool vector start point and the tip of the tool is displayed as a tool vector.
The tool used when machining a workpiece by a machine tool, other than a tool whose tip carries out machining, can be a tool whose side face machines a workpiece like an end mill. The surface of the product may be the surface which was machined by the side face of the tool. Accordingly, it is preferable that errors with respect to the design value of the machined surface machined by the side face of the tool be small. For example, it is preferable the error between the actual position of the tool or inclination thereof be small with respect to the movement command of the tool.
The error when the machined surface is machined by the side face of the tool corresponds to the error in the position or the posture of the axis of the tool. Accordingly, by estimating the error of the axis of the tool, the error of the machined surface can be estimated. For example, when the axis of the tool moves in compliance with a command value as instructed by the control device, the error of the machined surface will decrease.
In the above Japanese Patent No. 4689745, the tool vector can be displayed. However, the trajectory of the axis of the tool when cutting a workpiece at a predetermined flat plane cannot be displayed. As it is difficult to confirm whether or not the trajectory of the axis of the tool is the desired trajectory for the portion machined by the side face of a tool, there is room for improvement.